To identify the characteristic ultrasonographic findings of the normal appendix in children in order to detect it more easily and so to exclude acute appendicitis from a diagnosis with more confidence.

Among 64 patients presenting with right lower quadrant pain, 44 patients, excluding 15 patients diagnosed as acute appendicitis and 5 patients with non-visualization of the appendix due to severe ileus and obesity, were evaluated for the point of incidence, the thickness and the presence of folding of the inner hypoechoic band of the normal appendix. The age of the patients ranged from 3 to 15 years with a mean age of 6.5 years. Two patients were operated on and we correlated the preoperative ultrasonographic findings with the histologic findings.

In all the cases of the 44 patients with normal appendix, the inner hypoechoic band was discovered, which was seen as a linear structure without folding along the whole length of appendix. This measured as 0.75 mm (0.3-1.5 mm) for the mean thickness. The inner hypoechoic band corresponded to the mucosal layer that had abundant lymphoid tissue on the histologic examination.

For the pediatric normal appendix, the inner hypoechoic band without folding is present, and this corresponds to the mucosal layer with abundant lymphoid tissue.